mircury lna™ microrna ish optimization kit … · mir-126-3p ish signal is seen in endothelial...

miRCURY LNA™ microRNA ISH

Optimization Kit (FFPE)

Instruction manual v3.0 for product # 90000, 90001, 90002, 90003,

90004, 90005, 90007, 90008, 90009

January 2016

Detection

2

miRCURY LNA™ microRNA ISH Optimization Kit (FFPE) · Instruction Manual

Abbreviations. FFPE: formalin-fixed and paraffin-embedded. ISH: In situ hybridization. LNA™: locked nucleic acid. Prot-K: Proteinase-K. RT: room temperature. AP: alkaline phosphatase. DIG: digoxigenin. PFA: paraformaldehyde.

Table of contents

Product Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Product summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Kit content . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Shipping and storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Additional required material . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Reagents and equipment required, not supplied . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Product description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Before starting the experiment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Workflow overview - One-day microRNA ISH protocol. . . . . . . . . . . . . . . . . . . . . . . . . . 14

One-day microRNA ISH protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Tips and troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Frequently asked questions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Related products . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

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Product summary

Product summary

The miRCURY LNA™ microRNA ISH Optimization Kit (FFPE) provides the user with reagents

and recommendations to ensure the best starting point for successful microRNA in situ

hybridizations (ISH) on formalin-fixed paraffin embedded (FFPE) tissue samples. The kit

contains 3 digoxigenin (DIG)-labeled probes: one double- (5’ and 3’)-DIG labeled probe for a

known cell-specific microRNA, one double-(5’ and 3’)-DIG labeled Scramble-miR probe to use

as negative control, and one 5’-DIG labeled probe against U6 snRNA for use in the early-phase

assay set-up. In addition, the kit contains a formamide-free hybridization buffer developed

specifically for miRCURY LNA™ Detection probe-based ISH. The included Proteinase-K will allow

the user to optimize the Proteinase-K treatment for optimal retention of the microRNA target.

The accompanying One-day microRNA ISH protocol minimizes time-consuming optimization

steps and enables a fast and optimal microRNA ISH analysis using a colorimetric antibody-

based development system for the DIG labeled probes. In addition, the Instruction Manual

carefully covers each step of the FFPE ISH procedure, including tissue sectioning, incubation

intervals and temperatures, miRCURY LNA™ microRNA Detection probe concentrations and

substrate incubation. The manual further contains a list of recommended equipment and

reagents required to establish and optimize microRNA ISH in the lab.

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Kit content

Shipping and storage

Upon receipt

The kit is shipped at room temperature. Immediately upon receipt, remove the miRCURY

LNA™ microRNA ISH buffer from the box and store at 4°C. Store the DIG-labeled miRCURY

LNA™ microRNA Detection probes and Proteinase-K in the box at -20°C or below. Under

these conditions the probes are stable for at least 6 months. It is recommended to store the

probes in aliquots and to avoid multiple freeze-thaw cycles (see recommendations below).

Do not store in frost-free freezer with automatic thaw-freeze.

Before First Use

• Proteinase-K stock: reconstitute to 20 mg/mL by adding 600 µL 10mM Tris-HCl, pH7.5 (RNase-

free). Store appropriate aliquots at -20°C.

• DIG-labeled LNA™ probes: The following options are possible:

1) The probes may be stored at 4°C if used within 4 weeks.

2) Prepare aliquots to be stored at -20°C or below and avoid multiple freeze-thaw cycles.

Example: divide the LNA™ Detection probes into 5µL or 10µL aliquots into non-stick RNase-

free tubes.

3) Prepare pre-diluted probe aliquots to be stored at -20°C or below in the microRNA ISH buffer.

This option is only recommended once the optimal probe concentration has been determined.

For details of how to make 1x microRNA ISH buffer and how to denature and dilute the probes, please

see page 12. On the day of use, thaw the pre-diluted probe to room temperature and apply

directly to the sections. Note: Probe concentration must be optimized (see Tip 3, page 21).

Reagent Vol. Conc. RNA Tm

LNA™ microRNA probe, double-DIG labeled 40µL 25µM See datasheet

LNA™ Scramble-miR probe, double-

DIG labeled (5’-gtgtaacacgtctatacgccca-3’)40µL 25µM 87˚C

LNA™ U6 snRNA probe, 5’ DIG-labeled

(5’-cacgaatttgcgtgtcatcctt-3’)40µL 0.5µM 84˚C

microRNA ISH buffer (2x) 25mL

Proteinase-K, lyophilized 12mg

See Tip 3

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Additional required material

ISH protocols vary extensively due to different equipment set-up and laboratory routines.

This one-day miRCURY LNA™ microRNA ISH protocol details the process of manual ISH on

formalin-fixed and paraffin embedded tissue samples using double-DIG labeled miRCURY

LNA™ microRNA Detection probes.

For the ISH steps we recommend a hybridization station that allows precise and rapid temperature

adjustments, e.g. Dako Hybridizer. This protocol is developed using a hybridization station, but

if unavailable, conventional hybridization ovens may be used (see details in FAQs on page 26).

For the immunohistochemical steps Exiqon has had good experience with both horizontal

humidifying chambers and Shandon’s Sequenza Slide Rack systems.

The chromogenic ISH assay is based on the use of DIG-labeled probes and therefore requires

proper detection reagents (e.g. alkaline phosphatase-conjugated anti-DIG and NBT-BCIP

substrate).

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Reagents and equipment required, not supplied

In addition to the reagents supplied in the miRCURY LNA™ microRNA ISH Optimization Kit,

a series of reagents as well as equipment are needed to perform the ISH experiments as

described in the protocol. The list below includes recommendations for specific products

that have been shown to work well with the microRNA ISH protocol (details of how to prepare

buffers and reagents can be found on page 10-13):

• Double-DIG-labeled miRCURY LNA™

Detection probes for your microRNA(s)

of interest (Exiqon)

• Sheep anti-DIG-AP (Roche,

Cat. No. 11 093 274 910)

• Sheep serum (Jackson

Immunoresearch,

Cat. No. 013-000-121)

• NBT/BCIP ready-to-use tablets (Roche,

Cat. No. 11 697 471 001)

or equivalent

• Levamisole

(Fluka, Cat. No. 31742 or equivalent)

• Syringe and Whatman 1.001-125 filter

paper for filtering nuclear counter

staining solution

• Nuclear counter stain, Nuclear Fast

Red™ (Vector laboratories,

Cat. No. H-3403 ) or equivalent

• Mounting medium, Eukitt® (VWR, Cat.

No. 361894G)

• RNaseZap® (Ambion)

• Hybridizer, e.g. Dako Hybridizer, Vysis’

ThermoBrite, or Invitrogen’s Spotlight

Hybridizer

• Humidifying chamber or equivalent for

immunohistochemical detection

• Superfrost®Plus slides

• Cover slips

• Slide rack(s) and several glass jars

for deparaffinization, dehydration, and

washes

• Xylene (for de-paraffination)

• Ethanol (for hydration and dehydration)

• PBS, sterile

• SSC buffer, ultrapure

• 1M Tris-HCl, pH 7.4

• 0.5M EDTA

• 5M NaCl

• Tween-20 (Sigma, cat no. P1379)

• 30% BSA (Sigma, cat no. A9576)

• For KTBT buffer: Tris-HCl,

NaCl and KCl (see page 11)

• Dako Pen (or equivalent hydrophobic

PAP pen)

• Non-stick RNase free microfuge tubes

• Sterile filter tips

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Product description

In situ hybridization (ISH) is a powerful technique and the most common method for visualizing

gene expression and localization in specific tissue and cell types. The technology is far from

trivial and is often a very time-consuming and difficult procedure requiring many steps of

protocol optimizing to achieve satisfactory ISH results. Detection of microRNA by conventional

ISH analysis is no exception.

The miRCURY LNA™ microRNA ISH Optimization kit (FFPE) offers a fast and robust procedure

for an easy implementation of microRNA ISH analysis requiring a minimum of optimization. The

microRNA ISH buffer is specifically developed for use with the double-DIG labeled miRCURY

LNA™ microRNA Detection probes. Used in combination, this provides the best available

method for specific and sensitive detection of microRNA expression by ISH in FFPE sections

of any tissue specimen.

The ISH protocol is designed for detection of microRNA in FFPE tissue sections and takes

advantage of the use of the non-mammalian hapten digoxigenin (DIG), and has been optimized

to fit into a one-day experimental set-up. During the protocol the microRNAs are demasked

using Proteinase-K, which allows the access of double-DIG-labeled LNA™ probes to hybridize

to the microRNA sequence (Figure 1). The digoxigenins can then be recognized by a specific

anti-DIG antibody that is directly conjugated with the enzyme Alkaline Phosphatase (AP). AP

converts the soluble substrates 4-nitro-blue tetrazolium (NBT) and 5-bromo-4-chloro-3’-

indolylphosphate (BCIP) into a water and alcohol insoluble dark-blue NBT-BCIP precipitate.

Finally, the nuclear counter stain is applied to the sections to allow better histological resolution.

LNA™ probe

MicroRNA

NBT-BCIP

Blue precipitate

DIG

AP

DIG

AP

Figure 1.

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Optimization of the ISH procedure is divided into three steps:

1. Optimization of the protocol parameters with the LNA™ U6 snRNA probe by adjustment of

hybridization temperature and Proteinase K treatment.

2. Control study using the optimized protocol parameters with the kit-specific double-DIG

LNA™ microRNA probe and LNA™ Scramble-miR negative control probe

(a strong specific ISH signal should be obtained).

3. Detection of the microRNA of interest using the appropriate miRCURY LNA™ microRNA

Detection probe.

Figure 2 shows a typical result of the microRNA ISH procedure. In this case, specific hsa-

miR-126-3p ISH signal is seen in endothelial cells, as expected no signal is observed with

LNA™ Scramble-miR probe, and overall nuclear staining is seen with LNA™ U6 snRNA probe.

Once optimized, the protocol allows exceptionally clear and specific detection of microRNA

at the cellular and partly subcellular level due to high signal-to-noise ratio. An excellent

histological resolution is obtained in a wide range of tissue samples. In fact, several different

kits are available, each with a unique positive control miRCURY LNA™ microRNA Detection

probe targeting a specific microRNA known to be highly expressed in a distinct organ or cell

type. This makes the kit ideal for a variety of applications ranging from study of microRNA

localization, developmental microRNA regulation, examination of functional studies over

diagnostic and prognostic biomarker discovery in clinical specimens and other biopsy material.

The robustness of the procedure makes it advantageous for both high-throughput ISH analysis

as well as individual microRNA localization studies.

hsa-miR-126-3p, 40nM Scramble-miR, 40nM U6 snRNA, 0.1nM

Figure 2. In situ hybridization on consecutive sections from FFPE tissue sample with human breast cancer

using the miRCURY LNA™ microRNA ISH Optimization kit 5 (FFPE) with the positive control miRCURY

LNA™ microRNA Detection probe, hsa-miR-126-3p.

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Before starting the experiment

In order to ensure that the lab, equipment and reagents for the microRNA ISH procedure

are in place before starting the experiment, it is recommended to go through the following

sequence of steps:

1) Prepare and store kit reagents (page 4).

2) Establish histology Lab environment for RNA work (page 9-10).

3) Prepare samples (including fixation of tissue and FFPE preparations, page 10).

4) Cut FFPE sections using Tissue Sectioning Guidelines (page 20).

5) Prepare reagents and buffers (page 10-12).

6) Become confident with the steps in the One-day miRCURY LNA™ microRNA

ISH protocol (page 14-19).

7) Evaluate appropriate Proteinase-K treatment range for each sample type.

8) Determine ISH sensitivity level using the LNA™ U6 snRNA probe. It may be necessary to

repeat Step 6 and 7 to gradually improve the performance of the protocol.

9) Run the microRNA ISH protocol with the LNA™ microRNA probe and LNA™

Scramble-miR probe.

10) Optimize hybridization temperature and probe concentration for each probe.

An overview of the workflow for the One-day miRCURY LNA™ microRNA ISH protocol is

shown on page 14.

Protocol

RNA work requires specific handling and precautions to prevent RNase contamination

of the reagents and degradation of the RNA sample.

Every step in the microRNA ISH procedure including tissue sectioning and DIG-detection,

must take place in a clean and nuclease free environment. We recommend that all surfaces

are cleaned with RNaseZap®, RNase Away or other RNase removal solution. Wear gloves

during the entire process, and only use RNase decontaminated glassware. All buffers and

reagents should be prepared using RNase-free water only, e.g. RNase-grade Milli-Q water

or DEPC-treated water, and be autoclaved if specified.

Important note - Cautions for RNA work

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FFPE sample requirements and comments on tissue fixation

MicroRNAs are like other RNA fragile molecules sensitive to degradation. Fast and sufficient

fixation of tissue specimens is therefore important for successful ISH analyses. For ISH analysis

in human specimens, standard overnight fixation in neutral-buffered formalin followed by paraffin

embedding often works well. For studies in mouse tissues, perfusion fixation with 4% fresh PFA

is recommended before standard overnight fixation in formalin. Consult animal care guidelines

before setting up this protocol, see e.g. The Laboratory Mouse by Mark A. Suckow, Peggy

Danneman, Cory Brayton (CRC Press) or Pathology of Genetically Engineered Mice by Jerrold

Michael Ward, Joel F. Mahler, Robert R. Maronpot (Iowa State University Press). Optimization

of the assay performance should preferably be based on analysis of at least 4 FFPE blocks. For

detailed guidelines to Tissue Sectioning, please see Tip 1, page 20.

Glassware

In order to reduce potential RNase contamination of glassware, it is recommended to autoclave

all glassware or to heat-treat all glassware for 8 hours at 180°C. Prior to the heat-treatment,

it is recommended to wrap all items in aluminum foil, including appropriate stacks of cover

slips. Keep apart from untreated glassware.

Preparation of reagents and buffers

In addition to the hybridization buffer and Proteinase-K buffer supplied with the microRNA ISH

Optimization Kit, a number of other reagents and buffers need to be prepared prior to initiating

the microRNA ISH experiment (see page 6 for a list of recommended materials). Recipes for

preparation of required reagents and buffers are listed in Table 1-3.

See Tip 1

Please notePlease note that many reagents should be freshly prepared on the day of the experiment or even

immediately before use.

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Buffers and stocks to prepare and autoclave* prior to the microRNA ISH experiment

Proteinase-K buffer

To 900 mL RNase-free water add

5 mL of 1 M Tris-HCl (pH7.4)

2 mL of 0.5 M EDTA

0.2 mL of 5 M NaCl

Adjust volume to 1000 mL. Autoclave*.

20xSSC pH 7.0 If purchased as RNase-free then leave as is.

SSC solutions

5xSSC (1 L=250 mL 20xSSC + 750 mL water)

1xSSC (1 L=50 mL 20xSSC + 950 mL water)

0.2xSSC (1 L=10 mL 20xSSC + 990 mL water) Autoclave

PBS-T (0,1%), pH7.4 Add 1 mL of Tween-20 to 1 L of PBS. Autoclave*.

KTBT (AP stop solution)

To 900 mL RNase-free water add

7.9g Tris-HCl (50mM)

8.7g NaCl (150mM)

0.75g KCl (10mM)

Adjust volume to 1000mL. Do not adjust pH. Autoclave*.

*autoclave buffers where listed to minimize RNase activity. RNaseAlert® Lab test Kit (Ambion) is an easy and fast test that is recommended for optional testing of potential RNase activity in buffers and reagents.

Reagents needed during the ISH procedure

Antibody blocking solutionPBS, 0.1% Tween, 2% Sheep serum, 1% BSA,

(see table 3 for details)

Antibody dilutant solutionPBS, 0.05% Tween, 1% sheep serum, 1% BSA (see table

3 for details)

Sheep-anti-DIG-AP See table 3

NBT/BCIP ready-to-use tablets See table 3

LevamisoleFor blocking endogenous AP activity.

Prepare a 100 mM stock

Nuclear Fast Red™ Nuclear counter stain

Table 1.

Table 2.

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Reagents to prepare on the day of the experiment

Proteinase-K reagent

Prepare immediately before use. For a Proteinase-K

concentration of 15 µg/mL: Add 7.5 µL Proteinase-K stock to

10 mL Proteinase-K buffer (prepared in Table 2). See further

recommendations in Tip 2, page 20.

Hybridization mix

(microRNA ISH buffer

and LNA™ Detection probes)

1) Dilute the 2x microRNA ISH buffer 1:1 with RNase-free water,

e.g. mix 1 mL 2x microRNA ISH buffer with 1 mL RNAse-free

water to give 2 mL 1x microRNA ISH buffer.

2) For each probe to be used in the experiment, place the

appropriate amount of LNA™ probe in a 2 mL non-stick

RNase-free tube (see table below).

3) Denature the probes at 90°C for 4 minutes.

4) Place the tubes in table-top microfuge and spin down shortly.

5) Immediately add the 2 mL 1x microRNA ISH buffer to each of

the tubes with the different LNA™ probes.

Probe Final probe

conc.

Probe vol. Dilution

factor

1x microRNA

ISH buffer vol.

LNA™ U6 snRNA (0,5µM) 1 nM 4 µl 1:500 2 ml

LNA™ microRNA probe (25µM)* 20 nM 1,6 µl 1:1250 2 ml

LNA™ microRNA probe (25µM)* 40 nM 3,2 µl 1:625 2 ml

LNA™ Scramble-miR

probe (25µM)

40 nM 3,2 µl 1:625 2 ml

* Suggested starting concentrations for microRNA probes can be found in Table 8, page 22.

Table 3.

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Antibody blocking and

Dilutant solutions

1) To make 10mL blocking and 10mL dilutant solution start with

15mL PBS-T (see table 2) and add 300µL Sheep serum (2%

final concentration). Label the tube “Blocking solution”

2) Remove 5 mL from the tube in Step 1, place in a new tube and

label “Dilutant solution”.

3) To the tube labeled Blocking solution, add 330µl 30% BSA to

give a final concentration of 1%. The blocking solution is now

ready to use.

4) To the tube labeled Dilutant solution, add 5 mL PBS (to give

0.05%Tween and 1% sheep serum final concentration) and

330µl 30% BSA to give 1% final concentration. The Dilutant

solution is now ready for use.

Anti-DIG reagentDilute the sheep-anti-DIG-AP antibody 1:800 in Antibody Dilutant

solution (see above). (Range 1:500-1:2000).

AP substrate

Immediately prior to use, dissolve a NBT-BCIP tablet in Milli-Q

water according to the manufacturer’s instructions. Add

Levamisol to a final concentration of 0.2 mM.

Example: if 10 mL AP substrate is prepared, then add 20 µL

Levamisol stock. Protect from light before and during incubation.

Please noteleft over hybridization mix can be stored at -20°C and will be stable for up to 6 months, avoid

multiple freeze-thaw cycles

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Workflow overview - One-day microRNA ISH protocol

* PBS washing steps are excluded from the overview. Total time required is 7 hours.

Slide rack and Jars 40 min. Room Temperature

Room Temperature

Room Temperature

10 min. 37°C

50-60°C

50-60°C

30°C

30 min.

15 min.

60 min.

120 min.

10 min.

5 min.

10 min.

60 min.

Hybridizer

Hybridizer

Water bath

IHC staining racks

IHC staining racks

Slide rack and Jars

IHC staining racks in Oven

Deparaffi nation

Proteinase-K

In situ hybridization

Stringent washes

Blocking

Anti-DIG/AP

AP reaction

Counter stain

Dehydration

Mounting

Process* Equipment Time TemperatureStep

1

6

14

9

17

2

8

16

4

11

Below is an overview of the workflow for the microRNA ISH protocol for FFPE samples. The

numbers refer to each of the steps in the protocol, see details in the protocol section, page

15-19. The workflow can be followed for both the initial protocol optimization with the LNA™

probes provided with the kit and the subsequent specific microRNA detection.

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One-day microRNA ISH protocol

Step 1

Deparaffinize slides in

xylene and ethanol

Deparaffinize slides in xylene and ethanol solutions at room

temperature (RT) by placing slides with sections in a slide rack, and

then move from glass jar to glass jar according to Table 4 ending up

in PBS.

Table 4.

Step Solvent Duration

1 Xylene 5 min.

2 Xylene 5 min.

3 Xylene 5 min.

4 99.9% Ethanol Immerse 10 times


6 99.9% Ethanol 5 min.

7 96% Ethanol Immerse 10 times

8 96% Ethanol 5 min.



11 PBS 2-5 min.

The protocol describes every step in the microRNA ISH analysis. When setting up the microRNA

ISH experiment for the first time it is recommended to follow the three optimization steps:

1) First, optimize the protocol parameters with the LNA™ U6 snRNA probe by adjustment of

hybridization temperature and Proteinase-K treatment.

2) Conduct control study using the optimized protocol parameters with the double-DIG LNA™

microRNA positive and negative control probes. Adjust hybridization temperature and

Proteinase-K treatment to obtain a strong specific microRNA ISH signal.

3) Finally, detect the microRNA(s) of interest using the appropriate miRCURY LNA™ microRNA

Detection probe(s) with the defined protocol parameters keeping in mind that the hybridization

temperature may need to be adjusted.

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Step 3

Place slides in PBS

Place slides into a slide rack inside a jar with PBS, wash twice in PBS.

Step 2

Incubate with

Proteinase-K for

10 min. at 37°C

Immediately before use, add Proteinase-K to Proteinase-K buffer (see

Table 2 & 3). Place slides on a flat surface and apply approximately

300 µL/slide to fully cover the section and incubate slides for 10 min.

at 37°C for example in a Dako Hybridizer. If the Hybridizer is used then

remove the humidifying strip inserts.

The Proteinase-K concentration range must be optimized for

individual tissues (see Tip 2).

Step 5

Disassemble slide

and coverslip

Prepare a jar with 5xSSC at RT. One by one, carefully remove the

coverslip and immediately place the slide into a slide rack in the

5xSSC buffer. If the coverslips do not easily detach, place the slides

directly into the 5xSSC buffer. After a few minutes the coverslips will

detach and the slides are transferred into the jar containing 5xSSC.

Step 4

Apply hybridization mix

and hybridize for 1 hour

at 50-60°C

Place slides on a flat surface and apply 50 µL hybridization mix

as prepared in Table 3. For initial protocol optimization, probe

concentrations could be:

a) 1 nM LNA™ U6 snRNA probe

b) 40 nM double-DIG LNA™ microRNA probe

The probe concentration will need to be optimized for optimal

microRNA ISH signal. See Tip 3.

Avoid touching the tissue sections with the pipette tip. Then apply a

sterile coverslip onto each section, carefully avoiding air bubbles.

Place the slides in the Hybridizer (equipped with humidifying strips

hymidified with Milli-Q water) and start a program hybridizing for

1 hour. Hybridization temperature must be optimized for individual

probes, see Tip 4).

See Tip 2

See Tip 3+4

17


Step 6

Wash slides in SSC

buffers

Wash slides in glass jars according to Table 5. To ensure sufficient

stringency perform the washes in glass jars placed in a water bath

set to the hybridization temperature.

Table 5.

Step Buffer Duration Temperature

1 5xSSC 5 min. Hyb temp



4 0.2xSSC 5 min. Hyb temp

5 0.2xSSC 5 min. Hyb temp

6 0.2xSSC 5 min. RT

Step 7

Apply hydrophobic

barrier

Transfer slides to glass jars with PBS.

Apply a hydrophobic barrier around tissue sections using a

Dako-Pen following the manufacturer’s instructions. Tissue

sections are not allowed to dry out during this and the subsequent

immunohistochemistry steps. Alternatively, if Shandon Slide Racks

are employed, then assemble slides on coverplates using PBS-T.

Step 8

Incubate with blocking

solution for 15 min.

Place the slides in a humidifying chamber and incubate 8 with

blocking solution for 15 min. at RT. Important: Steps 8-15 are carried

out in the humidifying chamber or in Shandon Slide Racks.

Step 9

Apply anti-DIG reagent

for 60 min.

Remove blocking solution and apply anti-DIG reagent (sheep anti-

DIG-AP at 1:800 in antibody dilutant, see Table 3) and incubate for 60

minutes at RT.

Step 10

3x3 min. wash in PBS-T

Wash the slides 3x3 minutes with PBS-T.

18


Step 12

Incubate slides in KTBT

buffer 2x5 minutes

Incubate slides in KTBT buffer 2x5 minutes to stop

the reaction.

Step 11

Incubate with AP substrate

for 2 hours at 30°C

Apply freshly prepared AP substrate to the sections (see Table 3)

and incubate slides for 2 hours at 30°C in the humidifying chamber.

Protect from light during development.

Step 13

Wash with water, 2x1 min.

Wash with water, 2x1 minutes.

Step 14

Counter stain with

Nuclear Fast Red™

Depending on the size of the tissue, apply 200-300 µL Nuclear

Fast Red™ (nuclear counter stain) for 1 minute for nuclear counter

staining. Right before application, it is recommended to pass the

Nuclear Fast Red™ solution through a paper filter (e.g. Whatman

1.001-125) to remove undissolved color precipitates.

Step 15

Rinse in tap water

for 10 min.

Remove slides from the humidifying chamber to a slide rack placed

within a glass jar containing tap water. Carefully rinse the slides with

running tap water for app. 10 min.

19


Step 16

Dehydrate slides

Dehydrate slides in ethanol solutions according to Table 6.

Place the slides on clean paper towels.

Table 6.

Step Solvent Duration






6 99.9% Ethanol 1 min.

Step 17

Mount slides

Mount the slides directly with 1-2 drops of mounting medium

(Eukitt®). Avoid air-drying sections at this step.

Step 18

Microscopy

Allow precipitate to settle overnight and analyze results by light

microscopy the subsequent day.

20


Tips and troubleshooting

Tip 1. Tissue Sectioning Guidelines

It is strongly recommended to wear gloves during paraffin sectioning and in general to maintain

an RNase-free environment during all downstream procedures. Use only heat-treated glassware

and RNase-free water. Use SuperFrost®Plus slides drawn directly from new packages.

Workstation and Microtome

Before starting the tissue sectioning, the whole workstation (bench top, microtome, blade holder,

brushes, tweezers, cooling plate, water bath etc.) needs to cleaned with RNase-Zap/RNase Away.

Cutting sections

1) Prepare a water bath with room temperature RNase-free water and a warm-water bath with

RNase-free water at 40-50°C (depending on the paraffin type).

2) Insert a new disposable blade in the knife carrier and place the paraffin block in the cassette

clamp. Trim the block in order to avoid the first couple of sections. It is recommended to cool

the FFPE blocks on a cooling plate to app. -15°C before cutting to better control the section

thickness.

3) Cut 6 µm-thick paraffin sections and place them in the room temperature RNase-free water,

where folding can be reversed. Transfer the sections to the heated water bath, where the

tissue section is allowed to stretch shortly. It is recommended to mount sections immediately

thereafter on electrostatic treated slides, such as SuperFrost®Plus slides, obtained from a

new non-contaminated package.

4) Let the paraffin sections dry for 1-2 hours at room temperature and store at 4°C for up to one

week. Avoid melting the paraffin until the day prior to the in situ hybridization analysis.

5) Melt paraffin in an oven at 60°C for 45 minutes on the day before conducting the ISH experiment.

Store slides overnight at 4°C in an RNase-free environment.

Tip 2. Identify appropriate Proteinase-K treatment range

The degree of Proteinase-K treatment depends on fixation and tissue of origin. In general terms,

the harder the fixation, the more Proteinase-K is needed, however there are lower and upper

limits. For the Proteinase-K treatment step, it is recommended to vary the concentration or

the duration, as indicated in Table 7. Optimal (opt) starting values are shown in parenthesis.

21


Tip 3. Identify ISH sensitivity level

In order to identify the sensitivity of the performance of the ISH protocol, it is recommended to

prepare dilutions of the LNA™ U6 snRNA probe. Figure 3 shows that the LNA™ U6 snRNA probe

should provide a significant ISH signal at 0.03 to 0.3nM concentration. It is recommended that

U6 snRNA ISH signal is intense (as shown for 0.1 nM concentration in Figure 3), when the probe

is incubated at 0.1-2.0 nM before moving on with the double-DIG probes for microRNA ISH.

Table 7.

To identify the optimal Proteinase-K conditions, start by testing the LNA™ U6 snRNA probe at 4-5

different concentrations between 0.1-2.0 nM using the One-day microRNA ISH Protocol. Once

the conditions have been established, start testing the double-DIG labeled LNA™ microRNA

probe (positive microRNA control) and the LNA™ Scramble-miR probe (negative control).

Adjust concentration

Fixation Temperature Proteinase-K, Duration

human FFPE routine formalin 37°C 5-20 µg/mL (15) 10 min.

mouse FFPE PFA perfusion 37°C 0.5 - 5.0µg/mL (2) 10 min.

Adjust duration

Fixation Temperature Proteinase-K,

conc

Duration (opt)

human FFPE routine formalin 37°C 15µg/mL 5-30 min. (10)

mouse FFPE PFA perfusion 37°C 2µg/mL 3-30 min. (10)

22


Once the optimal hybridization conditions are achieved for the LNA™ U6 snRNA probe, it is

recommended to use the suggested starting concentrations in Table 8 for the double-DIG labeled

miRCURY LNA™ microRNA Detection probes supplied in the microRNA ISH Optimization Kits,

(optimal hybridization temperature is in the 50-60°C range).

0.3nM 0.1nM 0.03nM 0.01nM 0.003nM no probe

*optimization range for the double-DIG LNA™ probe could be 20-80 nM.

Figure 3. Optimization of positive control probe, LNA™ U6 snRNA, detection signal. On consecutive

sections from FFPE tissue sample from normal human colon, the hybridization conditions are optimized

by application of increasing concentrations of the postive control probe, LNA™ U6 snRNA.

Table 8. miRCURY LNA™ microRNA Detection probe, suggested concentrations*

(positive control as supplied with the Kit)

Probe name Concentration, nM RNA Tm

hsa-miR-1-3p 20 81°C

hsa-miR-21-5p 20-40 83°C

hsa-miR-122-5p 40 85°C

hsa-miR-124-3p 40 90°C

hsa-miR-126-3p 40 84°C

hsa-miR-145-5p 20 84°C

hsa-miR-205-5p 20-40 87°C

hsa-miR-223-3p 40 83°C

23


Tip 4. Identify optimal hybridization temperature

Optimal performance of an ISH probe is related to its signal-to-noise ratio. Oligonucleotide probes,

and especially LNA™ containing probes, can potentially hybridize to highly similar sequences if

the hybridization temperature is too low. The positive control LNA™ probes supplied with the

microRNA ISH Optimization kit typically result in a high signal-to-noise ratio at 55°C using the

One-day miRCURY LNA™ microRNA ISH protocol. The LNA™ probes also hybridize at 60°C,

but generally provide weaker signals. At 50°C the LNA™ probes give stronger signals, but the

risk of cross-hybridization to highly similar sequences (in RNA transcripts or the genome) will

increase at low hybridization temperatures.

As a rule-of-thumb, hybridization should be performed at 30°C below the given RNA Tm (or

20°C below DNA Tm

).

24


Troubleshooting

No signal: If no signal is obtained with the LNA™ U6 snRNA probe incubated at 10 nM, it is

recommended to ensure that all reagents are prepared according to the recommendations and

are RNase free (pages 9 and 11-13). Always test sections from more than one block (a minimum

of 4 is recommended).

Not sufficient sensitivity level with the LNA™ U6 snRNA probe. It is recommended that the

LNA™ U6 snRNA signal is intense when incubated in the range of 0.1-1 nM. If this is not the case,

ensure that the buffers are prepared correctly and that tissue sections are in the range 5-7 µm.

Ensure that the AP-reaction takes place at 30°C. Low sensitivity may also be caused by RNase

contamination during sectioning or handling during the in situ hybridization protocol. Make sure

all steps of the ISH protocol are performed in an RNase-free environment. Be aware that both

insufficient or hard fixation of tissue samples may result in a low signal. Thus, it is necessary

to test several blocks in parallel and avoid concluding on a single sample.

Strong U6 snRNA signal but no or low microRNA signal. If a strong U6 snRNA signal is obtained

with 0.1-0.5 nM probe, but no signal is obtained with the supplied positive control LNA™ microRNA

probe, it is most likely due to sub-optimal Proteinase-K treatment. Hence, the Proteinase-K

concentration or duration of treatment should be optimized (see Tip 2 for details). In order to

boost a weak signal, remove the anti-DIG reagent in Step 9 halfway through the incubation (e.g.

after 30 minutes) and apply new unused reagent for the second half of the incubation. The same

approach can be used for the AP substrate in Step 11. For low copy number targets it may be

possible to increase the signal with Tyramide Signal Amplification (TSA) based systems.

Non-specific staining. It is necessary to clarify whether non-specific staining obtained with the

LNA™ Scramble-miR probe is related to the DIG-labeled probe itself, the detecting antibody

or to endogenous enzymatic reactions. This can be done by a systematic approach where

the effect of excluding individual reagents is tested including the DIG-labeled probe, the AP-

conjugated anti-DIG or both. If staining is obtained in the absence of AP-conjugated anti-DIG

then endogenous AP is present.

25


If staining is obtained in the absence of the DIG-labeled probe (and no endogenous AP activity is

observed) then staining is related to the detecting antibody. If abundant endogenous enzymatic

reactivity (e.g. in some intestinal areas and placenta) cannot be prevented by Levamisol, it may

require a change to another detection approach, such as TSA-based fluorescence (see e.g.

Nielsen and Holmstrøm, Methods Mol. Biol., 2013).

Some non-specific staining can be caused by improperly maintained SSC wash buffer

temperatures. It is important to ensure that the SSC wash buffers are preheated to and

maintained at the hybridization temperature (see Step 6, page 17).

High background staining. Providing all possibilities for non-specific staining mentioned above

have been ruled out and as long as the specific signal from the microRNA probe is strong, high

background signal can often be reduced by increasing the hybridization temperature and/or

increasing the duration of the stringency washes.

Non-specific staining of ECM. Non-specific staining of extracellular matrix may occur if the

concentration of the detecting antibody is too high.

Sections fall off after de-paraffination. Avoid storage of paraffin sections at -20°C.

Small and thick sections fall off more easliy than large thin sections. Ensure that the

glass slides used have electrostatic properties such as the SuperFrost®Plus slides.

When transferring sections from the waterbath to slides it is important to let all excess

water drain/evaporate from the section and slide to avoid water or air bubbles getting

trapped under the section. For fatty tissues or loose connective tissue e.g. tissue from

normal breast, increasing the duration of the melting step from 45 minutes to 60 minutes

sometimes helps.

26


Frequently asked questions

Can I use a hybridization oven instead of a Dako Hybridizer? When using a hybridization oven

during the hybridization step, it may be advisable to seal the coverslips using Fixogum. The

slides can be placed as such in the hybridization oven without humidifying conditions. However,

humidifying conditions may be tried, e.g. by using 1xSSC buffer. In order to establish a more

stable hybridization temperature place a metallic plate, e.g. the inserts from a multiblock

heater, in the oven. Place the slides on the plate and hybridize for 1–2 hours. Then go to Step 5.

Can I use the protocol for fresh frozen tissue? The protocol can be adapted to cryo sections

(Nielsen et al., Methods Mol. Biol,. 2014), please find guidelines for fresh frozen samples at

www.exiqon.com/mirna-ish-kit. The protocol will require optimization for individual sample

types and microRNA targets.

Can I pause the ISH procedure? The individual steps in the One-day protocol have been optimized

to accommodate a One-day protocol. PBS steps may be prolonged, but it is not recommended

to extend the protocol to more than one day.

What happens if sections dry out? Sections should be maintained in buffered solutions after

the hybridization step. Tissue sections that dry out may cause protein denaturation, which

may be particularly harmful to the detecting antibody and its conjugated alkaline phosphatase.

This may lower the sensitivity of the assay significantly and in addition cause background

staining. Drying out of tissue sections may also reduce the quality of the tissue morphology.

Can I use other detection methods? The DIG labeled LNA™ probes can be detected using

alternative methods for DIG detection such as the TSA based systems. The use of alternative

systems may necessitate additional steps to be added at various stages of the protocol and

requires optimization. Please go to www.exiqon.com/mirna-ish-kit for more information.

27


Can I detect two different microRNAs in the same section? Two microRNAs can be detected in

the same FFPE section by double fluorescence analysis. It may also be possible using double

chromogen detection; however, this has not been documented.

For the double microRNA staining assay, two miRCURY LNA™ microRNA Detection probes

with different labels (haptens) are required, such as one LNA™ probe double-labeled with

DIG and one LNA™ probe double-labeled with FAM, or alternatively DIG and Biotin labels.

Fluorescence detection of microRNAs is performed using peroxidase-conjugated sheep

antibodies and Tyramine substrates (TSA), such as TSA-Cy3 (red fluorophore) and TSA-FITC

(green fluorophore). ISH can be performed by mixing the two probes. However, if different

hybridization temperatures are required for optimal hybridization, or if the two probes interact,

hybridization should be performed consecutively. After the two probes have hybridized, one of

them is detected with a peroxidase-conjugated antibody (e.g. anti-DIG) followed by incubation

with an appropriate TSA substrate (e.g. TSA-FITC). After a peroxidase blocking step (in 3%

H2O2), the other probe is detected with the proper peroxidase-conjugated antibody (e.g. anti-

FAM) followed by another TSA substrate (e.g. TSA-Cy3). All steps need optimization, including

stringent washes and washes in PBS after antibody incubations. The staining intensity should

be significant, and should be evaluated against negative control sections in order to adjust for

background staining and autofluorescence. The slides can be mounted with DAPI mounting

medium.

In the study by Sempere et al. (Clin. Cancer Res. 2010), miR-205 was co-detected with U6 snRNA

using double FAM and double biotin labeled miRCURY LNA™ microRNA Detection probes,

respectively. miR-205 and U6 snRNA signals were revealed by sequential TSA reactions with

TSA-FITC (green for miR-205 probe) and TSA-rhodamine (red for U6 snRNA probe) substrates.

28


Can I detect both microRNA and protein in the same section? A microRNA can be detected

together with a protein in tissue sections by combined ISH and immunohistochemistry double

fluorescence staining. The main limitation in such an assay is the compatibility of pretreatment

procedures required for the microRNA probe and the primary antibody. MicroRNA ISH is limited

to protease-dependent pretreatment, and therefore some literature searches may be needed

to identify an appropriate primary antibody that works well with proteolytic pretreatment. It

is recommended to evaluate the performance of the antibody prior to use in the ISH study.

Alternative strategies may involve cryo sections, in which microRNA ISH can be performed

(Nielsen et al., Methods Mol. Biol., 2014) and most primary antibodies can be applied without

pretreatment.

For the combined microRNA ISH and immunohistochemistry, the microRNA in situ hybridization

is performed at first, essentially as described in this protocol. The probe is detected with a

peroxidase conjugated antibody (e.g. anti-DIG) followed by an appropriate TSA substrate (e.g.

TSA-FITC). After stringent washes, the sections are incubated with the primary antibody (e.g.

rabbit-anti-cytokeratin) followed by a proper fluorophore-conjugated antibody (e.g. Cy3-

conjugated anti rabbit). The One-day microRNA ISH protocol using miRCURY LNA™ microRNA

Detection probes has been described in detail by Nielsen and Holmstrøm (Methods Mol. Bio.,

2013). The slides can be mounted with DAPI mounting medium.

Can I use other types of double labeling as alternative to double DIG? The original microRNA

ISH protocol was developed using DIG-labeled miRCURY LNA™ microRNA Detection probes

(Jorgensen et al, Methods, 2010). However, the miRCURY LNA™ microRNA Detection probes

can be obtained with other labels as well, including FAM and biotin. Detecting AP-conjugated

antibodies (anti-FAM or anti-biotin), or streptavidin for biotin, must then replace the anti-DIG

antibody. The double FAM-labeled LNA™ probes show the same signal-to-noise as the double

DIG-labeled LNA probes and can be used equally well. The concentration of the miRCURY

LNA™ microRNA Detection probe and the detecting antibodies should always be optimized

for best performance regardless the choice of label type.

29


Related products

Exiqon offers a broad variety of products enabling new discoveries concerning the isolation,

expression, function and spatial distribution of microRNAs:

miRCURY LNA™ microRNA Detection Probes

For in situ hybridization and northern blotting of all annotated microRNAs.

miRCURY LNA™ microRNA ISH Buffer Set

Hybridation buffer and Proteinase K for continuation of the optimized ISH procedure with

miRCURY LNATM microRNA Detecion probes.

miRCURY™ RNA Isolation Kits

Get high quality total RNA suitable for miRCURY LNA™ microRNA Array analysis in as little

as 20 minutes. Protocols are available for a large number of sample types and organisms.

miRCURY LNA™ microRNA Array System

miRCURY LNA™ microRNA Arrays for global microRNA expression profiling, complete with

all required reagents and Hi-Power Labeling Kits.

miRCURY LNA™ Universal RT microRNA PCR

Exiqon’s microRNA qPCR system offers the best available combination of performance and

ease-of-use on the microRNA real-time PCR market. The combination of a Universal RT

reaction and LNA™-enhanced PCR primers results in unmatched sensitivity and specifi city.

The Ready-to-use microRNA PCR panels enable fast and easy microRNA expression profiling.

Pre-validated individual assays and custom assays are also available.

miRCURY LNA™ microRNA Inhibitors and Power Inhibitors

Unravel the function of microRNAs by microRNA inhibition. Sophisticated LNA™ design ensures

potent inhibition of all microRNAs regardless of their GC content. Chemically modified, highly

stable Power Inhibitors for unrivalled potency.

30


miRCURY LNA™ microRNA Inhibitor Library

For genome-wide high throughput screening of microRNA function.

miRCURY LNA™ microRNA Mimics

Highly potent mature LNA™-enhanced microRNA mimics with unique triple RNA strand design.

miRCURY LNA™ microRNA Target Site Blockers

High-affinity LNA™-enhanced microRNA target site blockers (TSBs) for the study of single

microRNA target sites.

31


• Robust One-day in situ hybridization protocol for detection of microRNA in paraffin

samples using LNA probes. Jørgensen S, Baker A, Møller S, Nielsen BS. Methods (2010),

52, 375-381.

• Chromogen Detection of microRNA in Frozen Clinical Tissue Samples Using LNA™ Probe

Technology. Nielsen BS, Møller T, Holmstrøm K. Book chapter in “In Situ Hybridization

Protocols” in the Methods in Molecular Biology series (2014), 1211, 77-84.

• Combined MicroRNA In Situ Hybridization and Immunohistochemical Detection of Protein

Markers. Nielsen BS, Holmstrøm K. Book chapter in “Target Identification and Validation

in Drug Discovery”. Methods and Protocols” in the Methods in Molecular Biology series

(2013), 986, 353-65.

• Fluorescence-based codetection with protein markers reveals distinct cellular

compartments for altered MicroRNA expression in solid tumors. Sempere LF, Preis M,

Yezefski T, Ouyang H, Suriawinata AA, Silahtaroglu A, Conejo-Garcia JR, Kauppinen S,

Wells W, Korc M. Clin Cancer Res. (2010), 16, 4246-55

• The Laboratory Mouse. Mark A. Suckow, Peggy Danneman, Cory Brayton.

CRC Press, ISBN 0849303222.

• Pathology of Genetically Engineered Mice. Jerrold Michael Ward, Joel F. Mahler, Robert

R. Maronpot. Iowa State University Press, ISBN 0813825210.

• www.exiqon.com

References

32


Literature citations

Please refer to miRCURY LNA™ microRNA Detection probes and ISH Optimization kit when describing a procedure for

publication using this product or to the following article: Robust One-day in situ hybridization protocol for detection of

microRNA in paraffin samples using LNA probes. Jørgensen S, Baker A, Møller S, Nielsen BS. Methods (2010), 52,373-381.

Patents and Trademarks

Exiqon, LNA™ and miRCURY™ are registered trademarks of Exiqon A/S, Vedbaek, Denmark. Locked Nucleic Acids

(LNA™) are covered by patents and patent applications owned by Exiqon A/S. All other trademarks are the property of

their respective owners.

Locked-nucleic Acids (LNA™s) are protected by US Pat No. 6,268,490, US Pat No. 6,770,748, US Pat No. 6,639,059, US Pat

No. 6,734,291 and other applications and patents owned or licensed by Exiqon A/S.

Disclaimer

Products are for research use only and not for diagnostic or therapeutic use. The products in their original or any modified

form may be used only for the buyer’s internal research purposes and not for commercial, diagnostic, therapeutic, or other

use, including contract research. The buyer may not resell products in their original or any modified form. The purchase

of products does not include or carry an implied right or license for the buyer to use such products in the provision of

services to third parties and a license must be obtained directly from Exiqon A/S for such use.

© Copyright 2016 Exiqon. All rights reserved.

33


Outside North America

Exiqon A/S · Skelstedet 16

DK-2950 Vedbaek · Denmark

Phone +45 45 660 888

Fax +45 45 661 888

North America

Exiqon Inc. · 12 Gill Street, Suite 1650

Woburn, MA 01801 · United States

Phone (781) 376 4150

Fax (781) 376 4152

exiqon.com

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